Security paper or board product and security package

ABSTRACT

The invention relates to a method for producing a security paper or board product carrying micro or nano structures such as diffractive optical elements in which method the diffractive structures are integrated into the security paper or board product at the manufacturing process of said product. The invention also relates to a method for producing a security package carrying diffractive structures in which method the diffractive structures are integrated into the security package at a manufacturing stage of the security package material. The invention further relates to a security package containing authentication information in a form of diffractive structures in which package the diffractive structures are included in the security package at least in one of the following forms: as embossed in the package material, as part of the size or paste or resin used in the manufacturing process of the security package, or as part of the ink used in printing the security package or the security package material.

[0001] The present invention relates to a method for producing asecurity paper or board product or a security package carrying micro ornano structures such as diffractive optical elements for providinginformation for authentication. The present invention also relates to asecurity package containing authentication information in a form ofdiffractive structures.

[0002] Diffractive optical elements are optical components, whichcontain structures with dimensions of the order of wavelength of light.With diffractive optical elements it is possible to control propagationof light by macroscopically smooth surfaces containing micro or nanostructures. These structures are later referred as diffractivestructures. A simple example of a diffractive optical component is aone-dimensional diffraction grating consisting of periodic grooves ofthe order of wavelength. When white light beam is passed through orreflected from a diffraction grating it is dispersed in a spectrum.“Diffractive Optics for Industrial and Commercial Applications” (editedby Turunen and Wyrowski, Akademie Verlag 1997, ISBN 3-05-501733-1)discloses diffractive optics and components and their use and design.This source is later referred as “Diffractive Optics”.

[0003] It is known from prior art to use diffractive structures as wellas other optical security elements as watermarks in valuable documentsand products for authentication purpose. Diffractive optical securityelements are typically embossed on thin foils and applied on articles tobe marked as separate adhesives. Optical security objects can includevarious elements observable by various methods. According to“Diffractive Optics” these observation methods can be divided intofirst-line, second-line, and third-line inspection levels. First-lineinspection is based on the human senses only for instance vision,hearing and the tactile senses. General public who must be able todistinguish counterfeit and forgery mainly uses first-line inspectionthat can be performed by bare eye. In second-line inspection simpletools are used to reveal hidden security objects. Examples of thesetools are magnifiers, barcode scanners, laser pointers, ultravioletsources and automatic teller machines. Third-line inspection involvesforensic investigation of the security element performed by expertsusing advanced techniques and equipment. This kind of equipment is veryexpensive and is available only in few research institutes in the world.

[0004] Manufacturing of diffractive structures requires advanced andcomplex systems, which only are available in advanced laboratories.Therefore diffractive structures are very difficult to forge.

[0005] According to “Diffractive Optics” advantages for usingdiffractive structures as security elements are firstly, that they cannot be reproduced with colour copiers or modern desktop publishingequipment. Secondly, production of diffractive structures is quiteinvolved and it requires special equipment and knowledge. Thirdly, theoptically variable effects are generally quite noticeable and thereforethey adequately facilitate first line inspection.

[0006] Diffractive structures are usually manufactured bymicrolithographic methods. U.S. Pat. No. 4,662,653 discloses anoptically diffracting security element comprising a continuousreflecting surface, a dielectric layer formed contiguous with thereflecting surface, and a plurality of non-continuous reflecting surfaceportions embedded in the dielectric layer in a predetermined arrangementfor storing authentication information and a process for forming suchelement.

[0007] U.S. Pat. No. 5,862,750 discloses a method for impressionmicroengravings, which reproduce holograms, kinetic holograms ordiffraction patterns, directly on paper through an embossing process. Inthis method paper is subjected to a pre-treatment step prior toembossing said microengravings to paper. The required pre-treatment is ahumidification step, which gives to a paper a degree of humidity between60% and 80% of relative humidity. The humidified paper is then passedthrough an embossing group at a certain temperature and pressure.According to said publication it is not possible to impressmicroengravings directly on untreated paper.

[0008] U.S. Pat. No. 5,871,615 discloses security paper carrying asurface profile pattern imparted to the paper during its manufacturewhich requires de-watering of the paper when imparting the profilepattern and drying thereafter. The tactile surface profile pattern isvisible when viewed under low angle light, which facilitatesverification or authentication of security documents made using thepatterned paper.

[0009] U.S. Pat. No. 5,981,040 discloses a holographic image produced ofresinous ink comprising metallic particles. This special ink is used forprinting to a sensitive document to form a reflective coating, which isembossed by a shim. The embossed area of the reflective coating reflectslight in a slight different direction than the remainder of thereflective coating, thereby creating a holographic image.

[0010] U.S. Pat. No. 5,974,150 discloses an authentication systemcomprising a medium having a plurality of elements, which aredistinctive, detectable and disposed in an irregular pattern or havingan intrinsic irregularity. The system provides authentication of anobject by providing at least two levels of security, which are aphysical level, provided by an observable feature an authenticationcertificate, and an information level, provided by encoding a uniquecharacteristic of the authentication certificate (such as the observablefeature) and/or object to be authenticated in a marking on thecertificate.

[0011] U.S. Pat. No. 5,961,152 discloses security paper which has afilament bonded and embedded into paper which has been previouslymanufactured. The filament is bonded to the paper by an adhesive, or byheat and pressure. The filament may include a combination of securityfeatures, such as reflective filaments, fluorescent filaments, and hightensile strength filaments.

[0012] The problems with the prior art security objects are that theyare expensive to manufacture, difficult or expensive to integrate onpaper and easy to counterfeit if they are applicable as separateadhesive labels. Same applies to laminated package materials containingdiffractive foil layers.

[0013] The object of the present invention is to provide a securitypackage material and package that is inexpensive and fast to manufacturein amounts.

[0014] A further object of the present invention is to provide a methodfor embossing security elements directly into security package material.

[0015] A further object of the present invention is to provide a methodfor manufacturing security package material using existing machineryequipped with means for integrating diffractive structures into packagematerial.

[0016] A further object of the present invention is to provide a methodfor printing security markings directly on the packaging material byusing ink, dye, or other suitable colored or colorless painting liquidscontaining diffractive structures.

[0017] A further object of the present invention is to provide amanufacturing method for a packaging material containing diffractivestructures by using size or paste containing diffractive structures inthe manufacturing process of paper or board.

[0018] A further object of the present invention is to provide amanufacturing method for a packaging material containing diffractivestructures by using furnish containing diffractive structures in themanufacturing process of paper or board.

[0019] In view of achieving of the objectives stated above and thosethat will come out later the method for producing a security paper orboard product carrying micro or nano structures is mainly characterisedin that the diffractive structures comprise at least a section that isdetectable only by inspection tools and the diffractive structures areintegrated into the security paper or board product at the manufacturingprocess of said product.

[0020] A method for producing a security package carrying micro or nanostructures such as diffractive optical elements is characterised in thatthe diffractive structures comprise at least a section that isdetectable only by inspection tools and the diffractive structures areintegrated into the security package at a manufacturing stage of thesecurity package material.

[0021] Security package containing authentication information in a formof diffractive structures is characterised in that the diffractivestructures comprise at least a section that is detectable only byinspection tools and the diffractive structures are included in thesecurity package at least in one of the following forms: as embossed inthe package material, as part of the size or paste or resin used in themanufacturing process of the security package, or as part of the inkused in printing the security package or the security package material.

[0022] In prior art it is known to transfer diffractive structures topaper when remoisturing the paper first. According to the tests by theapplicant it has been found out that it is possible to emboss adiffractive structure directly on paper without any additional preparingstages which would require expensive stages to the paper making process.This embossing process can be integrated to several different parts ofpapermaking, finishing, converting, or printing process.

[0023] According to the invention diffractive structures used assecurity elements are included in the package itself by inserting theelements to the package material in the manufacturing stage. No furtherstages for adding security information is needed. The security elementscan be embossed onto the surface of the package material or they can beintegrated as small pieces in paste, size, resin, or furnish of thepaper or board or package material. Diffractive security elements canalso be mixed into the ink, dye, or painting liquids used in printingthe package.

[0024] The advantage of the present invention is the possibility tomanufacture security packages with low cost and with high securitylevel. This way forging the package is very difficult and various typesof security marks and security levels are easily available. The securityinformation can be included in any part of the package and it can be invisible form or in hidden form. Very large amount of informationpossible to include in a package when the method of the invention isapplied.

[0025] Because of the relatively low cost of producing the securitypackages according to the invention the present invention can beutilized in package industry manufacturing packages for consumerproducts liable to forgery, e.g. music CD's, computer products,medicines, cigarettes, or generally any brand products.

[0026] In a preferred embodiment of the invention a package bearingdiffractive structures with all security inspection levels is produced.

[0027] In the following the invention will be described in detail withreference of the figures in the accompanying drawing, the inventionbeing however by no means strictly confined to the details of saidembodiments or variations.

[0028]FIG. 1 shows an example of diffractive security structures.

[0029]FIG. 2 is a side view of a paper machine.

[0030]FIG. 3 is a schematic illustration of a calender nip for a papermachine.

[0031]FIG. 4 is a schematic illustration of a Condebelt drying system ofa paper machine.

[0032]FIG. 5 is a schematic illustration of a surface-sizing/pigmentingunit.

[0033]FIG. 6 is a schematic illustration of an extrusion coating line.

[0034] In embossing security elements to the package material in thepapermaking process an embossing surface containing plurality ofdiffractive structure shims is needed. A diffractive structure shim is ameans for embossing the diffractive structures to the desired material,such as paper or board or package material web. The diffractivestructure shims are preferably arranged in a suitably distributed matrixin the embossing surface, which is e.g. a roll in the paper machine orprinting unit as described later. For the shim matrix a desireddiffractive structure is first originated with an electron beam, a laserbeam, an X-ray beam, an ion beam, or other lithographic method to asuitable substrate coated with a proper resist. Thus a microscopicsurface relief profile is formed in the resist layer. Thereafter thesaid surface is transformed into a negative surface profile in nickel byelectroplating. The result is used to generate second and thirdgeneration shims for mass production. The process of manufacturing shimsis disclosed in detail in “Diffractive Optics”. Third generation shimsare then used in producing package material integrated with the desireddiffractive structures.

[0035] The method of embossing diffractive structures in securitymaterial is applicable to various kinds of paper, board, or packagematerial grades suitable for printing and packaging. Examples of theseare common paper (e.g. newsprint, SC paper, coated mechanical paper,uncoated fine paper, coated fine paper), paperboard (e.g. cartonboards,containerboards, special boards), specialty papers (e.g. cable paper,capacitor tissue, conductive paper, decor paper, photographic paper,building papers, sack kraft, flexible packaging, label paper). See“Paper and Board Grades”, part 18 in Papermaking Science and Technologyseries, ISBN 952-5216-1-7, for detailed information of these grades.

[0036]FIG. 1 shows an example of a diffractive security structuredivided into different security level elements. In this example thediffractive security structure contains areas for various securityinspection levels. In area A there is a figure that can be identifiedwith bare eye i.e. with first line inspection. Area A comprises twosecurity objects A1, A2. Object A1 is a simple wave pattern embossed inthe paper and it can be seen by bare eye. Object A2 contains text seenby bare eye at certain view angle when illuminated suitably. Text inobject A2 may also contain micro or nano structure information readableonly with a second or third level inspection tools.

[0037] In area B there is information that can be read with asecond-line inspection tool, such as a laser pointer. Area B comprisesmicro or nano dimensional security structures embossed in the material.A laser pointer LP is used for directing a laser beam to point x in areaB. Laser beam light diffracts from the security structure in point x andreveals a security structure B1.

[0038] Area C comprises micro or nano structures, which are onlyreadable by third level inspection, tools i.e. state-of-the-artequipment in research laboratories. An example of a security object C1revealed by such an inspection tool is shown. Object C1 is a micro scalebar code, which identifies the security, marked object. Alternatively,diffractive structures containing second and third line inspectionlevels can be hidden in various forms within the area covered by thearea of the first line inspection level structures.

[0039] In the method according to the invention for producing securitypaper or board or security packages diffractive structures are embossedto the package paper or cardboard as described above. In anotherembodiment of the present invention diffractive structures are includedin the paper or board product or in the security package material assmall pieces containing diffractive structures. In this methoddiffractive structures are embossed in thin sheets of a suitablematerial, such as aluminum or plastic foil. By grinding, cutting,crushing, or chopping embossed sheet to small pieces, chopped materialwith pieces containing diffractive structures is produced and thismaterial can be mixed to a raw material used in paper making or printingprocess. The chopped material can be mixed for instance to ink, size,paste, resin, or furnish.

[0040] When using furnish mixed with pieces containing diffractivestructures conventional paper and board making machinery can be applied.Using this approach in paper making process the produced paper orcardboard gets a glittering appearance, which is typical for diffractingsurfaces. Similarly well known sizing and coating methods can be usedwhen mixing pieces containing diffractive structures into size or paste.Also chopped material containing diffractive structures can be added toink which is then useable in any conventional printing system.

[0041] Suitable dimensions for chopped material with pieces containingdiffractive structures is of the order of 1 to 10 μm in ink, size, pasteand resin and up to 1 mm in furnish. Information contained in thediffractive elements can be read from security paper or board or packageaccording to the invention using special reading device. When using inkcontaining diffractive structures in printing of the security packagesthe text or pattern printed with diffractive ink contains information ofthe diffractive elements and also this information is readable withspecial reading equipment.

[0042] The method of embossing or printing the diffractive structuresdirectly on paper can be carried out e.g. in the following parts of thepapermaking or package manufacturing process:

[0043] on- or off machine calender unit

[0044] drying unit marketed by the applicant by the name Condebelt®

[0045] impulse drying unit

[0046] flexographic, gravure, offset, or other commercially availableprinting systems

[0047] extrusion coating lines

[0048] The method of adding chopped material containing diffractivestructures is applicable in the following parts of the papermaking orpackage manufacturing process:

[0049] stock preparation unit

[0050] sizing unit

[0051] coating unit

[0052] flexographic, gravure, offset, or other commercially availableprinting systems

[0053] extrusion coating lines

[0054] flexible package material lines

[0055]FIG. 2 shows a side view of a modern paper or board machine. Asshown in FIG. 2, stock is fed from a headbox 100 to a wire section 200followed by a press section 300. The web W is passed from the presssection 300 to a dryer section 400 followed by a soft-calendering unit500. The film-sizing unit 600 is used for treating the web.Surface-sizing, pigmenting, or coating is performed at this stagetypically on both sides of the web at the same time, but the surfaces ofthe web can also be treated separately in successive units. After that,the paper web is dried by using infrared dryers and airborne web-dryersand a short cylinder group, which follows them.

[0056] The web W is coated in coating stations 700, 800 which coat theweb W on both sides. After that, the web W is calendered in a multi-nipcalender 900, in which the linear load in each nip can be advantageouslyregulated separately. Finally, the web W is passed to a reel-up 1000 inwhich the web is wound into reels.

[0057]FIG. 3 shows an example of applying the method of embossingdiffractive structures to paper in a calender. In the calender anextended calendering nip N is formed between an upper roll 550 and ashoe roll 551. The shoe roll 551 comprises a press shoe 524 supported bya stationary beam 525 as well as a calendering belt 520 passed aroundthe press shoe 524 and the beam 525 and formed as an endless loop. Bymeans of the press shoe 524, the necessary load is produced in the nipN. According to the invention the upper roll 550 is coated with thediffractive structure shims and the diffractive structures aretransferred to the paper or cardboard web W passing the nip N. Inanother embodiment the calendering belt 520 is coated with diffractivestructure shims. Although a shoe calender has been described above thepresent invention can as well be applied into the prior art hard rollcalenders, soft calenders and supercalenders either on- or off- machine.

[0058]FIG. 4 shows a side view of a Condebelt drying system. Condebeltdrying system is known e.g. from patent publications FI-54514, FI-61537,and FI-101237. The Condebelt drying system is typically used incardboard machines. In the Condebelt drying system the web W carried ona fine-structured wire 43 and a coarse wire 44 is fed through a dryingunit 48, 49 between two smooth steel belts 41, 42. The upper steel belt41 contacting the web W is heated while the lower steel belt 42 iscooled. Subject to high pressure and temperature difference the moisturein the web W evaporates and the generated vapour traverses the wires 43,44 to condense on the cooler steel belt or the lower belt 42. Thecondensed water is taken out from the drying zone. This way dried webhas very advantageous strength characteristics combined with absence ofCD shrinkage. A smooth surface is obtained on one side of the web. Themethod according to the invention of embossing the diffractivestructures directly on paper or cardboard is applicable in the Condebeltdrying system by providing the heated metal belt wire with thediffractive structure shims.

[0059] In an impulse drying process, the web carried on the felt is fedthrough a pressing nip. The roll contacting the web is heated totemperatures well above 100° C. In this known process, a very smooth websurface can be obtained. According to one embodiment of the invention,the heated roll is provided with the diffractive structure shims totransfer the diffractive marking directly onto the web surface. Impulsedrying process is disclosed e.g. in U.S. Pat. No. 4,324,613.

[0060]FIG. 5 is a schematic illustration of an example of asurface-sizing/pigmenting unit 600, which is used for sizing and coatingpaper. Surface-sizing/pigmenting systems are disclosed e.g. in FI-93885and FI-81734. The surface-sizing/pigmenting unit 600 comprises rolls 602and 603 of the size press, so that the first roll 602 and the secondroll 603 form a nip N with one another, through which nip the paper orboard web W is passed. In the surface-sizing/pigmenting unit 600, afirst size film F₁ is metered onto the face of the first roll by meansof the first coating device 610 and, in a corresponding way, a secondsize film F₂ is metered onto the face 605 of the second roll by means ofthe second coating device 620. In the roll nip N, the size films F₁ andF₂ are transferred to the paper or board web W running through the nip.The coated web is denoted with the reference W′. The size films F₁ andF₂ are spread onto the faces 604 and 605 of the size press rolls 602,603 using bar coaters, which are equal to one another in this example ofa surface-sizing/pigmenting unit 600. In the coating devices 610, 620the coating agent is introduced into a pressurized coating-agent chamber616, 626 placed before the coating bar 611, 621. The coating bar 611,621 is fitted in a cradle 612, 622 supporting the coating bar 611, 621over its entire length and is rotated in directions opposite to thedirections of rotation of the rolls 602, 603. According to the inventionchopped material containing diffractive structures is added to size orpaste which is then transferred to the web in thesurface-sizing/pigmenting unit 600.

[0061] Extrusion is a process that transfers thermoplastics from a solidto a melted state and compresses them against a substrate using thepressure in a die. FIG. 6 shows an example of an extrusion coating line1200. A web (paper, aluminium or film) W is unwound from a main unwinder1210. The pre-treatment unit 1220 is used for pre-treating the web W ina way depending on the material e.g. in order to increase the adhesion.In the extrusion coating unit 1230 a melted resin (LDPE, PP, or other)is extruded on the web W with the extruder 1231. The resin is melted inthe extruder 1231 and through a flat die it is extruded on the web andimmediately cooled. The extrusion coating unit 1230 comprises a chillroll 1232 with chromium plated surface, a pressure roller 1233 with arubber surface, and a backup roller 1234 with chromium plated surface.

[0062] In the nip between the pressure roller 1233 and the chill roll1232 the extruded resin comes in contact with the web. The purpose ofthe chill roll 1232 is to reduce the temperature of the resin (normallyextruded at temperature ranging from 250° C. to 300° C.) to a valuebelow the melting point in order to prevent the sticking on the chillroll surface 1232.

[0063] As alternative it is possible to laminate two different webs inthe extrusion coating unit 1230 using the resin as adhesive. In thiscase the second web is coming from the secondary unwinder 1240. It ispossible to use more than one extruder if the product structure requiresdifferent layers. In this case the resins extruded from the extrudersare collected to the die through a feedblock. The purpose of thefeedblock is to collect the materials from the extruders maintaining thedifferent layers. The coated or laminated material obtained with thisprocess is rewound on the rewinder 1290. A thickness gauge 1250 isnormally placed before the rewinder 1290 to measure thickness variationof the final product to be rewound. An automatic control system can beused to manage the extrusion die in order to control the thickness ofthe extruded material.

[0064] The method according to the invention is applicable in anextrusion line preferably in the nip between the pressure roller 1233and the chill roll 1232. Either of the pressure roller 1233 or the chillroll 1232 is provided with diffractive structure shims according to theinvention. Alternatively, chopped material containing diffractivestructures is mixed with the extrusion coating resin.

[0065] The method according to the invention is also applicable in theprinting process of the security paper, board, or package. The printingprocess can be carried out in flexographic, gravure, offset, or othercommercially available printing systems. A printing machine isoptionally provided with an embossing unit, which is preferably placedin the printing line after the last printing unit. According to thepresent invention said embossing unit is provided with the diffractivestructure shims to transfer the diffractive marking directly onto theweb surface in the printing line.

[0066] In another embodiment of the present invention chopped materialcontaining diffractive structures is added to ink and then transferredto the printed material.

[0067] Alternatively, the method of embossing diffractive structuresdirectly on paper or board or package material according to theinvention is applicable to sheet material also. Sheets of paper, board,or package material can be embossed by stamping with a stamping device.A stamping device can be installed e.g. in connection with a sheetcutter in paper/board machine, printing machine, or such.

[0068] Laser pointers are preferable tools for inspecting theauthenticity of the security paper or board products or securitypackages according to the invention. Laser pointers are relativelyinexpensive and easy to carry along so they are available to public.When pointing a security marking according to the invention with a laserbeam special effects not seen with bare eye are revealed. These can bee.g. a company or brand logo appearing at or coming out from thesecurity marking.

[0069] The method according to the invention can be fully integrated tothe existing paper and cardboard machines and coating and printinglines. No auxiliary systems need to be built.

[0070] In addition of using the method according to the invention forproducing security marked material for authentication purpose the samemethod is applicable for decorative use.

[0071] In the following the patent claims will be given and variousdetails of the invention may show variation within the scope of theinventive idea defined in the patent claims and differ from the detailsdisclosed above for the sake of example only.

1. A method for producing a security paper or board product carrying micro or nano structures such as diffractive optical elements, characterised in that the diffractive structures comprise at least a section that is detectable only by inspection tools and the diffractive structures are integrated into the security paper or board product at the manufacturing process of said product.
 2. A method for producing a security package carrying micro or nano structures such as diffractive optical elements, characterised in that the diffractive structures comprise at least a section that is detectable only by inspection tools and the diffractive structures are integrated into the security package at a manufacturing stage of the security package material.
 3. A method according to claim 1 or 2, characterised in that the security paper or board product or security package material is paper, board, cardboard, corrugated board, printed paper, printed cardboard, or flexible package material comprising one or more layers of paper, plastic and/or metal.
 4. A method according to any of claims 1 to 3, characterised in that the method for producing security paper or board product or security package comprises a step of embossing diffractive structures to a security paper or board product or security package material web running through a nip between a forming surface containing the diffractive shim structure and a backing surface.
 5. A method according to any of claims 1 to 4, characterised in that the method for producing security paper or board product or security package comprises a step of embossing diffractive structures to a security paper or board product or security package material web in the Condebelt drying unit or in impulse drying unit.
 6. A method according to any of claims 1 to 5, characterised in that the method for producing security paper or board product or security package comprises a step of embossing diffractive structures to a security paper or board product or security package material in a printing unit.
 7. A method according to any of claims 1 to 5, characterised in that the method for producing security paper or board product or security package comprises a step of embossing by stamping diffractive structures to security paper or board product or package material sheets.
 8. A method according to any of claims 1 to 7, characterised in that the method for producing security paper or board product or security package comprises the steps of: manufacturing sheets containing embossed diffractive structures, chopping said sheets containing embossed diffractive structures to small pieces, mixing said pieces containing embossed diffractive structures to a raw material of security paper or board product or security package, manufacturing the security paper or board product or security package material using said raw material containing diffractive structures.
 9. A method according to claim 8, characterised in that the method comprises a step of mixing said pieces containing diffractive structures to furnish and/or paste and/or size and/or resin used in paper/cardboard manufacturing process.
 10. A method according to claim 8, characterised in that the method comprises a step of mixing said pieces containing diffractive structures to ink used in printing of the security paper or board product or security package.
 11. Security package containing authentication information in a form of diffractive structures, characterised in that the diffractive structures comprise at least a section that is detectable only by inspection tools and the diffractive structures are included in the security package at least in one of the following forms: as embossed in the package material, as part of the size or paste or resin used in the manufacturing process of the security package, or as part of the ink used in printing the security package or the security package material.
 12. A security package according to claim 11, characterised in that the security package is a cardboard package.
 13. A security package according to claim 11, characterised in that the security package is a flexible package.
 14. A security package according to claim 11, characterised in that the security package material is extrusion coated or laminated material.
 15. A security package according to any of claims 11 to 14, characterised in that the diffractive structures comprise sections for at least two inspection levels. 